1. Field of the Invention
The present invention relates to a human body sensing device to detect a human body and an image processing apparatus with this human body sensing device being mounted thereon.
2. Description of the Related Art
The following description sets forth the inventor's knowledge of related art and problems therein and should not be construed as an admission of knowledge in the prior art.
Some of the image forming apparatuses such as copiers, printers, and facsimiles, and some of the multifunctional digital image forming apparatuses referred to as MFPs (Multi Function Peripherals) collectively having copier, printer, and facsimile functions and the like are provided with a human body sensing device which is allowed to detect a human body approaching, so that they immediately can exit sleep mode to get back to normal operation mode for a warm-up operation when detecting a human body near themselves.
For example, there commonly known is a human body sensing device consisting of a pyroelectric sensor (also referred to as “pyroelectric infrared sensor”) with an energy-saving and low-cost configuration, being capable of performing human body detection.
When being installed on such an image processing apparatus, pyroelectric sensors are usually positioned in a certain manner so as to form a sensing area constituting a plane parallel with the direction in which a human body (user) approaches the image forming apparatus to use. However, the pyroelectric sensors usually are not very good enough to detect a human body moving across the sensing area because of too small changes in temperature. This is why there has been a considerable need for a human body sensing device achieving a higher accuracy in detecting a human body approaching.
Disclosed in Japanese Unexamined Patent Publication No. H10-160856 is a dual element pyroelectric sensor being characterized by outputting a signal whose phase is reversed when detecting a human body turning around, the dual element pyroelectric sensor being configured to identify the direction in which a human body is moving based on the waveform of its own signal.
Disclosed in Japanese Unexamined Patent Publication No. H06-088875 is a human body sensing device being provided with a pyroelectric element having two pyroelectric sensors fixed on one pyroelectric element plate, the human body sensing device being configured to have an intersection at an angle of 45 degrees induced by a horizontal floor and a virtual line connecting the two pyroelectric sensors, when being mounted on a vertical wall.
However, the technologies disclosed in the publications above would hardly be enough to achieve a higher accuracy in detecting a human body approaching, resulting in that there still needs to be such a human body sensing device.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. Indeed, certain features of the invention may be capable of overcoming certain disadvantages, while still retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.